Viscose spinning solution containing xanthated lower alcohol



2,993,798 VISCOSE SPINNING SOLUTION CGNTAINING XANTHATED LOWER ALCOHOL Friedrich Hildebrandt, Kassel-Bettenhausen, Germany,

assignor to Spinnfaser Aktiengesellschaft, Kassel-Bettenhausen, Germany No Drawing. Filed Aug. 27, 1956, Ser. No. 606,203 Claims priority, application Germany Sept. 13, 1955 6 Claims. (Cl. 106165) This invention in general relates to the production by the viscose process of cellulose filaments having low swelling values, high tearing and snarling resistance, and good crimping characteristics.

Rayon threads produced by the viscose process are composed of regenerated cellulose filaments. The cellulose usually comes from wood. In a typical viscose process, wood is chipped into small pieces, and the chips are threaded with a bisulfite salt such as calcium bisulfite. The treated chips are then cooked with steam under pressure for about 14 hours. This treatment does not greatly affect the cellulose, but it decomposes and solubilizes the encrusting substances, thus purifying the cellulose. The purified pulp is then bleached with hypochlorite and converted into paperboard. After conditioning the paperboard under definite humidity and temperature conditions, the sheets are stacked in a press and soaked with a strong solution of caustic soda (about 17.5% strength) from one to four hours. This process is known as steeping or mercerizing. The hemicellulose is dissolved in the caustic soda; the cellulose itself is swollen but not dissolved.

After the excess alkali is pressed out of the alkali cellulose, the moist mass is put through a shredding machine where it is broken up into fine crumbs. After shredding the crumbs are aged in contact with the atmosphere. Through oxidation by the atmospheric oxygen, degradive changes set in. Some depolymerization of the glucose residue in the cellulose molecule occurs, and the degree of polymerization falls from about 800 to 350 glucose residues per cellulose molecule. One process combines the shredding and aging steps by careful control of temperature and other physical conditions.

After aging, the alkali cellulose crumbs are introduced into rotating air-tight churns. About of their weight of carbon disulfide is added, and the crumbs and disulfide are churned up together. A deep orange gelatinous mass of sodium cellulose xanthogenate is formed. Churning is continued for several hours, and thereafter the sodium cellulose xanthogenate is stirred with dilute caustic soda solution for several additional hours at low temperatures. The xanthogenate dissolves to a viscous liquid similar in appearance to honey. This liquid is known as viscose, but it must be treated further before it is ready for spinning. The viscose contains in the vicinity of 5.57.0% alkali and 6.58.5% cellulose.

The viscose then is agitated in a secondary mixer or blender. Any undissolved fibers from the original wood pulp are removed by filtering the viscose. Air bubbles in the viscose solution are removed by drawing a vacuum on the viscose solution in air-tight tanks.

The viscose solution is next ripened for several days at low temperature. During the ripening, the viscosity first falls and then rises so that by the time the solution is ready for spinning the viscosity has risen almost to its original value. When the viscose solution is ripe all air bubbles are removed by exposure of the solution to vacuum. It is then forced by compressed air to spinning frames from whence it is metered by a small viscose pump to the spinning head. The spinning heads or spinnerettes are made from tantalum or one of the related metals and have a number of precision bored orifices f d States atent ice with a diameter usually between 0.05 and 0.1 millimeter. The spinnerettes are submerged in an acid bath which usually consists of sulfuric acid, sodium sulfate and zinc sulfate solutions. Sometimes glucose is also an ingredient. The filaments emerging from the orifices are solidified in the acid bath and as they emerge are passed over a series of rollers known as godets. The godets have roughened or serrated cylindrical surfaces, and the first 'godet is operated at a slower speed than the second whereby a stretch is imparted to the cellulose filament as it passes over the rollers without slipping. The filaments may be then passed into a second bath of more dilute acid and stretched further. The yarn filaments are then collected and purified by one or more of the following sequential steps:

(1) Washing.

(2) Desulfurizing.

(3) Bleaching.

(4) Washing.

The reaction of cellulose and caustic to give alkali cellulose is usually expressed:

(0 111005) n+7LNaOH (CaH904ONa) ri-nHrO Cellulose Alkali cellulose The reaction between the alkali cellulose and carbon disulfide may be represented:

S \SNZ. n

Alkali cellulose Alkali cellulose xanthate During the ripening period, some of the alkali cellulose xanthate decomposes, regenerating cellulose which is maintained in emulsion form by the portion of alkali cellulose xanthate still undecomposed. The conversion of the remainder of alkali cellulose xanthate to cellulose is accomplished in the acid spinning bath. The latter reaction of the xanthate portion of the polymer may be represented:

S [Cs 904OC\ 2S04- a 1o0s]+%NazSO4+CS2 SNa Alkali cellulose xanthate Regenerated cellulose Regenerated cellulose fibers having a low swelling value, high tearing and snarling resistance and characteristic constant crimping have not been produced in sufliciently high degree with the procedures known heretofore. Attempts to produce fibers with low swelling value and a smooth surface by various types of viscose blendings have introduced difficulties in control of conditions to produce such fibers. By the addition of monoarnines, fibers can be produced which have a thick mantle zone and are for this reason very resistant. It is, however, necessary to work with a high zinc sulfate content in the spinning bath of 3 to 4%; and it is necessary that other conditions of spinning be observed within a very narrow margin.

It is an object of this invention to provide improvements in viscose processes for manufacture of regenerated cellulose filaments.

A further object is to provide a process for producing regenerated cellulose fibers having physical properties adapting said fibers for wider uses than heretofore known.

Another object is to provide improvements in the viscose manufacture of regenerated cellulose whereby are produced filaments of improved tensile strength, improved resistance to tearing and snarling and improved crimping characteristics.

For the achievement of constant crimping it is necessary to produce in the preparation of the viscose itself the prerequisites for development of structural diiferences in fiber structure during the spinning and stretching process through which the crimping is brought about. Crimping imparts a Zig-zag pattern to the fibers instead of the usual straight form. I have discovered that cellulose fibers of low swelling value, high tearing and snarling resistance and good crimping characteristics can be produced by addition of small quantities of a lower aliphatic monohydric alcohol to the viscose solution. The viscose is thereupon spun in a bath containing zinc sulfate. Fibers produced in this manner have a bean-shaped crosssection, a strongly developed mantle zone and little or no serrations on the surface of the filament.

The alcohols employed are low molecular weight, aliphatic, monohydric alcohols of which methanol and ethanol are representative. Optimum results are usually achieved with about 2% by weight of alcohol, based on the weight of the alkali cellulose. Howeyer, there are occasions when it is desirable to use less alcohol or more alcohol. A general, economical range for the amount of alcohol employed would be about 0.54.0% of alcohol by weight based on the weight of the alkali cellulose. Especially successful results are obtained with methanol; the addition of an equal quantity of ethanol, however, also produces good results.

The conditions to be observed in the production of the viscose and in its spinning, such as the composition and ripeness of the viscose, sulfuric acid and zinc sulfate concentration of the spinning bath, as Well as the degree of stretching, are, by and large, subject to no particular regulation. It is easy to establish the optimum production conditions for the particular type of filament desired.

The alcohol can be added at any arbitrary point prior to the spinning step. Properly, stages of the processing are selected at which the blending is technically simple to accomplish. The alcohol can, for instance, be added to the alkali steeping solution, or to the alkali cellulose during the shredding step or immediately before mixing with carbon disulfide; it can also be added to the viscose after the alkali cellulose Xanthate is dissolved in dilute caustic. In the two first-mentioned cases a diminution in the rate of disintegration of the cellulose during aging occurs, which must be taken into consideration in the control of the viscosity.

If the alcohol is added at the end of the step wherein cellulose Xanthate is dissolved in dilute caustic, there is the advantage that no additional amounts of carbon dissulfide have to be used for the sulfidization of the alcohol. The alcohol Xanthate forms during the ripening step from carbon disulfide being released through splitting of the cellulose Xanthate groups, which carbon disulfide is thereby not used for side reactions and virtually lost, but, being bound to the alcohol, can develop a favorable effect as alcohol Xanthate. Furthermore, an acceleration of the ripening process is achieved. The various possible ways of carrying out the process permit an accommodation to the circumstances of the manufacture, as for instance, an influencing of the ripening process.

The considerable improvements of the fiber properties that can be achieved with simple means by the process according to the invention open new possibilities for the development and production of new types of fibers with characteristic valuable properties. In the following examples, the procedure is explained in detail:

Example I Beechwood sulfite pulp is sulfidized, after the addition of 1% by weight of methanol, based on the alkali cellulose, to the alkali cellulose, with 43%, on a dry basis of the cellulose, of carbon disulfide and dissolved to an 8.6/5.8 viscose. The methyl alcohol is sprayed onto the alkali cellulose immediately before the sulfidization and the alcohols carbon disulfide requirement taken into consideration with 6% (37% plus .6%:43%). At a ripeness of 13.0 to 14.0 H. with a gamma number of 38.0 to 39.0, the viscose is spun from 1800/60 n-nozzles to a 1.5 denier type of 40 mm. staple length.

The spinning bath contains 7.7 to 8.1% H SO and 0.8 to 0.9% of zinc sulfate at a temperature of 47 C. After an immersion stretch of 18 cm. the threads are conveyed immediately, by way of a godet or a glass rod, into a slightly acid, 96 to 98 C. second bath and there stretched by 70%. After cutting, the fibers are washed in a familiar manner and further processed. The tensile strengths of the fibers amount to 34.1 Reiss kilometers (Rkm.) (dry) and 21.2 Rkm. (wet); the stretching values to 17.1% (dry) and 21.3% (wet). The snarling resistance amounts to 7.7 Rkm. The crimping values, with 99 arcs/100 mm., a resistance to uncrimping of 58 mg, a crimping of 20.2% and a crimping constancy of 38.8%, are good. The fibers have a swelling value of 85. The fiber section is slightly serrated and shows a strongly developed, partly interrupted mantle zone.

Example II Beechwood sulfite pulp is sulfidized, after the addition of 1% by Weight of ethanol, based on the alkali cellulose, to the alkali cellulose with 43%, on a dry basis of the cellulose, of carbon disulfide and dissolved to an 8.6/5.8 viscose. The ethyl alcohol is sprayed on the alkali cellulose immediately before the sulfidizing and the alcohols carbon disulfide requirement taken into account with 6% (37% plus 6% :43% The viscose, at a ripeness of 13.0 to l4.0 H. with a gamma number of 38.0 to 39.0, is spun from 1800/60 n-nozzle to a 1.5 denier type of 40 mm. staple length.

The spinning bath contains 7.7 to 8.1% H 80, and 0.8 to 0.9% of zinc sulfate. It has a temperature of 47 C. After an immersion stretch of 18 cm. the threads are conducted by way of a godet or a glass rod, directly into a weakly acid, 96 to 98 C. second bath and there stretched by After the cutting, the fibers are Washed in a familiar manner and further processed. The tensile strength values of the fibers amount to 30.5 Rkm. (dry) and 19.9 Rkm. (Wet); the stretching values to 16.2% (dry) and 20.2% (Wet). The snarling resistance amounts to 7.4 Rkm. The crimping values, with arcs/100 mm., a resistance to uncrimping of 56 mg., a crimping of 13.6% and a crimping constancy of 38.5%, are good. The fibers have a swelling value of 87. The fiber section is bean-shaped and shows a strongly developed, uninterrupted mantle zone.

Example 111 Beechwood sulfite pulp, after the addition of 0.5% by weight of methanol, based on the alkali cellulose, to the alkali cellulose, is sulfidized with 40%, on a dry basis of the cellulose, of carbon disulfide and dissolved to an 8.6/5.8-viscose. The methyl alcohol is sprayed on the alkali cellulose immediately before the sulfidizing and the carbon disulfide requirement of the methyl alcohol is taken into account with 3% (37% plus 3%=40%). At a ripeness of 13.0 to 14.0" H. with a gamma number of 39.0 to 40.0, the viscose is spun from 1800/60 nnozzles to a 1.5 denier type of 40 mm. staple length.

The spinning bath contains 6.1 to 6.5% H 80 and 1.5 to 1.7% of zinc sulfate. It has a temperature of 47 C. After an immersion stretch of 18 cm. the threads are immediately conveyed by way of a godet or a glass rod into a weakly acid, 96 to 98 C. second bath and there stretched by 80%. After the cutting, the fibers are washed and further processed in a familiar manner. The tensile strength values of the fibers amount to 28.4 Rkm. (dry) and 18.3 Rkm. (wet); the stretching values to 14.8% (dry) and 16.5% (wet); the snarling resistance amounts to. 8.0 Rkm. The crimping values with 123 arcs/ 100 mm., a resistance. to. uncrimping of 68. mg, a

crimping of 18.4% and a crimping constancy of 33.8, are good. The fibers have a swelling value of 82.

Example IV Beechwood sulfite pulp, after the addition of 2% by weight of methanol, based on the alkali cellulose, to the alkali cellulose, is sulfidized with 46%, on a dry basis of the cellulose, of carbon disulfide and dissolved to an 8.6/5.8-viscose. The methyl alcohol is sprayed on the alkali cellulose immediately before the sulfidizing and the alcohols carbon disulfide requirement taken into account with 9% (37% plus 9%=46%). At a ripeness of 13.0 to 14.0 H. and a gamma number of 37.0 to 38.0, the viscose is spun from 1800/60 n-nozzles to a 1.5 denier type of 40 mm. staple length.

The spinning bath contains 6.1 to 6.5% H2804 and 1.5 to 1.7% of zinc sulfate. It has a temperature of 47 C. After an immersion stretch of 18 cm. the threads are immediately conveyed, by way of a godet or a glass rod, into a weakly acid, 96 to 98 C. second bath and there stretched by 90%. After the cutting, the threads are washed and further processed in a familiar manner. The tensile strength values of the fibers amount to 33.0 Rkm. (dry) and 21.8 Rkm. (wet); the stretching values to 16.1% (dry) and 17.8% (wet); the snarling resistance amounts to 8.3 Rkm.

The crimping values with 128 arcs/100 mm., a resistance to uncrimping of 69 mg., a crimping of 21.3% and a crimping constancy of 28.9%, are to be regarded as remarkably good. The fibers have a swelling value of 85.

Example V Beechwood sulfite pulp is alkalized; the alkali cellulose is sulfidized with 37%, on a dry basis of the cellulose, of carbon disulfide; and the xanthate obtained is dissolved in an 8.6/5.8 viscose. To the completely dissolved viscose, 0.25% by weight of methanol, with reference to the viscose, is added and mixed into it. At a ripeness of 9.5 to 105 H. and a gamma number of 33.0 to 34.0, the viscose is spun from 1800/ 60 n-nozzles to a 1.5 denier type of 40 mm. staple length.

The spinning bath contains 6.1 to 6.5% H SO and 0.8 to 0.9% of zinc sulfate. It has a temperature of 47 C. After an immersion stretch of 18 cm. the threads are directly conveyed, by way of a godet or a glass rod, into a weakly acid, 96 to 98 C. second bath and there stretched by 80%. After the cutting, the fibers are washed and further processed in a familiar manner. The tensile strength values of the fibers amount to 28.0 Rkm. (dry) and 18.7 Rkm. (wet); the stretching values to 13.3% (dry) and 18.0% (wet); the snarling resistance amounts to 8.0 The crimping values with 115 arcs/ 100 mm., a resistance to uncrimping of 79 mg., a crimping of 16.7% and a crimping constancy of 42.4%, are very good. The fibers have a swelling value of 84.

Thus, the present invention provides improvements in viscose processes for the manufacture of regenerated cellulose fibers having physical properties adapting the fibers for wider uses in manufacture of fabrics of regenerated cellulose fibers (rayons) and fabrics of blends of 60 regenerated cellulose fibers with natural fibers such as 6 cotton or wool or other synthetic fibers. The adaptation of fibers made according to the processes of this invention to these wider uses can be attributed to the improved tensile strength, the improved resistance to tear ing and snarling, and the inherent crimping of the filaments attained in the spinning and stretching operations.

The invention is hereby claimed as follows:

1. A viscose spinning solution made by sulfidizing alkali cellulose to which has been added an amount in the range of about 0.54% by weight based on the alkali cellulose of a lower molecular weight, aliphatic, monohydric alcohol of the formula ROH, wherein R is an alkyl group of 1-2 carbons.

2. A viscose spinning solution made by sulfidizing alkali cellulose to which has been added an amount in the range of about 0.5-4% by weight based on the alkali cellulose of methanol.

3. A viscose spinning solution made by sulfidizing alkali cellulose to which has been added an amount in the range of about 0.54% by weight based on the alkali cellulose of ethanol.

4. A viscose spinning solution made by sulfidizing alkali cellulose, said spinning solution containing xanthated methanol in the quantity, expressed as methanol, of about 0.54% by weight based on the original amount of alkali cellulose in said viscose spinning solution prior to sulfidization thereof.

5. A viscose spinning solution made by sulfidizing alkali cellulose, said spinning solution containing xanthated ethanol in the quantity, expressed as ethanol, of about 0.5-4% by weight based on the original amount of alkali cellulose in said viscose spinning solution prior to sulfidization thereof.

6. A viscose spinning solution made by sulfidizing alkali cellulose, said spinning solution containing a xanthated alcohol of the formula ROH, wherein R is an alkyl group of 1-2 carbons in the quantity, expressed as the alcohol, in the range of about 0.5-4% based on the original amount of alkali cellulose in said viscose spinning solution prior to sulfidization thereof.

References Cited in the file of this patent UNITED STATES PATENTS Scherer et al.: Rayon Textile Monthly, October 1942, pp. 59 to 60.

Groggins: Unit Processes in Organic Synthesis (1952), pp. 642 to 644.

Hermans: Physics and Chemistry of Cellulose Fibers 

1. A VISCOSE SPINNING SOLUTION MADE BY SULFIDIZING ALKALI CELLULOSE TO WHICH HAS BEEN ADDED AN AMOUNT IN THE RANGE OF ABOUT 0.5-4% BY WEIGHT BASED ON THE ALKALI CELLULOSE OF A LOWER MOLECULAR WEIGHT, ALIPHATIC, MONOHYDRIC ALCOHOL OF THE FORMULA ROH, WHEREIN R IS AN ALKYL GROUP OF 1-2 CARBONS. 